The present invention generally relates to machine tools, more particularly relates to apparatus for automatically loading machine tools, and in particular to an apparatus for automatically loading machine tools which operate on sheet or plate including a CNC punch press machine tool, a CNC punch press machine tool having a thermal cutting apparatus such as a plasma torch or a laser, a plasma cutting machine tool or a laser cutting machine tool.
FIGS. 1 and 2 are provided for background, and show a well-known type of punch press with thermal cutting capability, associated with a loader mechanism. The punch press is representative of the broad range of machine tools with which a loader according to the present invention can be associated. In greater detail, FIG. 1 shows machine tool 1, a CNC punch press having a loading apparatus 2. CNC punch press 1 has an X-axis 3 based on a rail 3xe2x80x2 supported by bracket 4 and pedestals 5 and 5xe2x80x2, carrying a translatable table 6.
Translatable table 6 is driven by a servomotor and ballscrew that cannot be seen and carries two workclamps 7 and 7xe2x80x2 for gripping the work, and several sets of punching tools 8. The Y-axis is defined by a frame 9 carrying a translatable punching cylinder 10 and a translatable die support 11. Punching cylinder 10 is driven via a servomotor 200 connected by coupling 201 to ballscrew 202. At the left side and connected to the mounting plate of punching cylinder 10 is a plasma torch 203 for cutting large holes and the outer boundary of parts from workpiece 17. Below and to the immediate left of torch 203 is a drop leaf table apparatus 204 for removal of small parts after they have been cut from material 17. An electrical cabinet houses the CNC 12 along with other electrical controls, and operator station 13 provides the man/machine interface for machine tool 1. Worktable 14 on the right side of frame 9 and worktable 15 on the left side of frame 9 and drop leaf table 204 are adapted with ball transfers 16 to support the material 17 to be processed. Material 17 is flat, rectangular metal sheet and plate.
In operation, material 17 is gripped by workclamps 7 and 7xe2x80x2 and moved and positioned under CNC control along X axis 3 while punching cylinder 10 and die support 11 are moved and positioned under CNC control along the Y-axis. The work is positioned and tools are selected according to a part program processed by the CNC 12. At commanded positions the CNC 12 cycles punching cylinder 10 to punch a hole in the work. After all holes have been punched the CNC 12 in like manner positions the plasma torch 203 to commanded positions, lowers plasma torch 203 to the work 17, ignites plasma torch 203 then coordinates the velocity and motion of the X and Y axes to move plasma torch 203 along a described path to create a hole or to cut a part from material 17. Small parts cut from the material are unloaded via drop leaf table 204 and large parts are removed manually, with the assist of a hoist or crane, or by other means.
A supply of material 17 is staged on loading apparatus 2 at the right side of machine tool 1. Loading apparatus 2 typically includes a base 77xe2x80x2 having a freestanding column 18 supporting a power driven cantilevered beam 19, pivotable at the proximal end of cantilevered beam 19 about supporting point 20. Cantilevered beam 19 is often further strengthened by a support rod 21, connected to cantilevered beam 19 at 22 and pivotally connected to column 18 directly above and inline with supporting point 20. Carried at the distal end of cantilevered beam 19 is a pivotable member 23, which is pivotable about bearing 24. In the illustrated embodiment two bearings 24 are mounted to plates 24xe2x80x2 bolted to the distal end of beam 19, one attached to the upper side of beam 19 and one to the bottom side of beam 19. The angular position of pivotable member 23 relative to machine tool 1 is fixed by a four bar linkage to stabilize the pivotable member 23 so as to maintain the long side of rectangular material 17 generally parallel to the X axis 3 of machine tool 1.
The first bar of the four bar linkage is attachment plate 25, which is connected to freestanding column 18. The second bar is bar 26 pivotally connected to attachment plate 25 and pivotally connected to pivotable member 23. The third bar is bar 27 pivotally connected to attachment plate 25 and pivotally connected to pivotable member 23. The fourth bar is the pivotable member or extension 23.
In the present embodiment, part handling apparatus generally indicated at 29a include mast 28 which is carried by and connected to pivotable member 23, and is adapted to support and vertically translate load beam 29 via cylinder 30. Bars 31 are adjustably connected to load beam 29 and are adapted with vacuum cups 31 xe2x80x2 to pick up material 17.
The powered drive for the cantilevered beam 19 is shown as a cylinder 32, which is pivotally connected at 33 to a plate 34 attached to freestanding column 18, and pivotally connected to cantilevered beam 19 at 35. Curved line 36 traces the path of the center of the mast as cantilevered beam 19 is pivoted by cylinder 32. Line 37 generally traces the path of the front edge of material 17 as it is transferred from the staging position to worktable 14 and workclamps 7 and 7xe2x80x2 of machine tool
When commanded to load a sheet of material, cylinder 30 lowers the vacuum cups to the supply of material 17. A sensor detects the presence of a sheet for pickup. The vacuum cups are engaged to grip the top sheet, cylinder 30 lifts the load beam picking up the top sheet of material, cylinder 32 pivots cantilevered beam 19 clockwise until the sheet is over worktable 14, cylinder 30 lowers the load beam and attached sheet to the surface of worktable 14, cylinder 32 pivots cantilevered beam clockwise to urge the sheet into the workclamps and toward workclamp registration surfaces 39xe2x80x2 and 39. Sensors associated with workclamp registration surfaces detect the sheet is loaded and cause the workclamps to grip the sheet. Then the vacuum cups release the sheet, cylinder 30 lifts the load beam and vacuum cups above the sheet, and cylinder 32 pivots cantilevered beam 19 counterclockwise positioning it once more over material 17 at the staging area.
While loader apparatus 2 can reliably deliver sheets of material to worktable 14 of machine tool 1, it cannot reliably load the material into workclamps 7 and 7xe2x80x2 in a registered orientation. If the sheet 17 in the supply stack is perfectly aligned with the X-axis of the machine tool, the four bar linkage is designed to deliver the sheets to the workclamps in parallel alignment with the X-axis as desired. But very often the sheet in the supply stack is not perfectly aligned, and therefore delivery into the workclamps is not reliably accomplished.
FIG. 2 is an enlarged drawing of the material loading side of machine tool 1 showing a fragment of machine tool 1. Like objects are identified with the same numbers as in FIG. 1. Workpiece 17, FIG. 2, is shown residing in an angular relationship to the X-axis of machine tool 1. Such conditions can occur several ways. The sheet may have been improperly stacked in preparation, the stack of material may have been jostled during transport, or the stack may have been improperly loaded on the loader staging station.
Workpiece 17xe2x80x2, FIG. 2, represents workpiece 17 after it is loaded on worktable 14. Note that the left end of sheet 17xe2x80x2 is in contact with registration surface 39xe2x80x2 while the right end is not in contact with registration surface 39. Loader 2 is a typical machine tool quality device with typical machine tool accuracy and repeatability, and it therefore lacks adequate compliance to successfully load the angular sheet. Loader apparatus 2 will stall at the position shown in which the sheet is not fully registered with the workclamps.
The problem exemplified in FIG. 2 is but one example of a condition that can cause failure of an automatic load cycle. Any condition in which the sheet is angularly rotated relative to the X-axis of machine tool 1 can cause similar load failure.
It is an objective of the invention to add controlled compliance to a loader, such that it can automatically and reliably load a sheet or plate into the workclamps of a CNC machine tool such as a punch press, while minimizing additional hardware and cost to do so.
Broadly, it is an object of the invention to provide an automated loader for a machine tool which cooperates with the machine tool to load the sheet or plate in a position which is registered along at least one axis. Such automated loading is accomplished without the need to move the workclamps along that axis during the loading operation.
It is a further objective of the invention to automatically gauge or position the loaded sheet such that the sheet can be processed by the CNC machine tool.
It is a feature of the invention that controlled compliance is added to a loader by providing a releasable four bar linkage.
It is a further feature of the invention to make one link of a four bar linkage pivotable and to provide a mechanism to alternately lock the link in position and release to the link such that it is free to pivot.
In that regard, a further feature is to restrict the range of motion of the releasable link of the four bar mechanism when it is in the released position.
A further objective of the invention is to provide a releasable four bar linkage that is easily adapted to other embodiments of loading or loading/unloading apparatuses.
Another objective of the invention is to provide a preferred embodiment of a loading device that can also be used to unload completed parts from a machine tool.